title: Does ritodrine worsen maternal hypotension during epidural anesthesia in gravid ewes?
abstract: The purpose of this study was to determine whether prior administration ritodrine worsens maternal hypotension during epidural anesthesia in gravid ewes. Twenty-four experiments were performed in nine chronically instrumented animals between 0.8 and 0.9 of timed gestation. The experimental sequence included the following: 1) at time-zero, intravenous (iv) administration of ritodrine, 0.004 mg.kg-1.min-1, or normal saline (NS) for 2 h; 2) at 120 min discontinuation of ritodrine, and administration of a 500 ml iv bolus of NS over 15 min; and 3) at 135 min epidural injection of 2% lidocaine or NS. There were three groups of experiments: 1) iv ritodrine-epidural lidocaine (n = 9); 2) iv NS-epidural lidocaine (n = 8); and 3) iv ritodrine-epidural NS (n =7). Epidural injection of lidocaine resulted in a median sensory level of T9 in both the ritodrine-lidocaine and NS-lidocaine groups. At 165 min (i.e., 30 min after the epidural injection of lidocaine), maternal mean arterial pressure was 19 +/- 3% below baseline (P = 0.0001) in the ritodrine-lidocaine group and 22 +/- 7% below baseline (P = 0.0001) in the NS-lidocaine group (NS between groups). At 120 min ritodrine had increased maternal cardiac output 45 +/- 6% above baseline (P = 0.0001) in the ritodrine-lidocaine group and 39 +/- 6% above baseline (P = 0.0001) in the ritodrine-NS group. Cardiac output remained above baseline (P less than 0.01) after epidural injection of lidocaine in the ritodrine-lidocaine group. In contrast, in the NS-lidocaine group cardiac output was 13 +/- 5% below baseline (P = 0.005) at 150 min. Fetal arterial pH did not change significantly in either the ritodrine-lidocaine or ritodrine-NS group.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: University of Iowa College of Medicine, Department of Anesthesia, Iowa City 52242.
authors.forename: D H
authors.initials: DH
authors.lastname: Chestnut
authors.forename: K L
authors.initials: KL
authors.lastname: Pollack
authors.forename: C S
authors.initials: CS
authors.lastname: Thompson
authors.forename: C S
authors.initials: CS
authors.lastname: DeBruyn
authors.forename: C P
authors.initials: CP
authors.lastname: Weiner
mesh_terms: D000767:Anesthesia, Epidural / Q000009:adverse effects*; D000773:Anesthesia, Obstetrical / Q000009:adverse effects*; D000818:Animals; D004347:Drug Interactions; D005260:Female; D006340:Heart Rate, Fetal / Q000187:drug effects; D006439:Hemodynamics / Q000187:drug effects; D007022:Hypotension / Q000139:chemically induced*; D008012:Lidocaine / Q000633:toxicity*; D011247:Pregnancy; D012312:Ritodrine / Q000633:toxicity*; D012756:Sheep
chemical_list: D008012:Lidocaine; D012312:Ritodrine